Newspaper article The Canadian Press

Researchers Probe Link between Bariatric Surgery and Higher Colon Cancer Risk

Newspaper article The Canadian Press

Researchers Probe Link between Bariatric Surgery and Higher Colon Cancer Risk

Article excerpt

Study probes bariatric surgery-colon cancer link

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TORONTO - Bariatric surgery has been a boon to obese patients hoping to shed significant pounds or to treat weight-related diabetes, but the downside is an increased risk of developing colon cancer. Now researchers believe they may know why.

The surgery significantly reduces the amount of food a person can eat by reconfiguring the digestive pathway. But by bypassing much of the stomach and small intestine, the food that is consumed isn't completely broken down when it reaches the large intestine, or colon.

And that appears to stimulate overproduction of a gut hormone that may spur the growth of polyps in the colon that have a propensity to become malignant, suggests Dr. Daniel Drucker, an endocrinologist at Mount Sinai Hospital in Toronto.

In studies in laboratory mice, a research team led by Drucker found the digestive hormone GLP-1 was "a pretty potent growth factor" for the intestine in the animals, as well as a catalyst for intestinal tumours in other lab mice specially bred to study colorectal cancer.

"If we gave the mice more GLP-1, they got more tumours," said Drucker, a senior scientist at the hospital's Lunenfeld-Tanenbaum Research Institute. "If we took away the GLP-1 receptor from those mice, genetically, they got fewer tumours.

"So this gets us pretty convinced that we're onto something."

The concern about colon cancer made headlines in 2013 when a Swedish-U.K. study of more than 77,000 obese patients showed that those who had undergone bariatric surgery had a 60 per cent increased risk of developing the malignancy compared with the general population.

Among people who had the surgery more than 10 years before the study's conclusion, the number of cancer cases was 200 per cent higher than what was expected for the population as a whole; obese subjects who had not had the operation had a 26 per cent higher risk of colon cancer than the general population, but that figure remained stable over time.

Since the risk of developing many other cancers fell with the weight-loss surgery, doctors were puzzled at the rise in colon cancer risk.

While Drucker is quick to point out that mice aren't humans, he said the animal studies go a long way in providing a biological explanation. …

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